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High Throughput Analysis of Liquid Droplet Impacts
Published on: March 6, 2020
Mixing and internal dynamics of droplets impacting and coalescing on a solid surface
J R Castrejón-Pita1, K J Kubiak, A A Castrejón-Pita
1Department of Engineering, University of Cambridge, 17 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|September 17, 2013
Summary
Mixing of impacting and sessile liquid droplets on surfaces is complex. Researchers found no mixing for similar-sized droplets, but vortex rings formed when one droplet was much larger, and wettability gradients could improve mixing.
Area of Science:
- Fluid Dynamics
- Surface Science
- Microfluidics
Background:
- Droplet impact and coalescence are fundamental phenomena in various applications, including inkjet printing and microfluidic devices.
- Understanding droplet mixing dynamics is crucial for controlling processes and achieving desired outcomes.
Purpose of the Study:
- To experimentally and numerically investigate the coalescence and mixing of sessile and impacting liquid droplets on a solid surface.
- To explore the influence of droplet size, impact velocity, and surface wettability on mixing efficiency.
Main Methods:
- Utilized two droplet generators for distinct droplet colors and two high-speed imaging systems for simultaneous side and bottom views.
- Employed a lattice Boltzmann framework calibrated with experimental contact angle measurements to model droplet dynamics.
Main Results:
- No significant mixing was observed during the impact and coalescence of similar-sized droplets.
- Vortex ring generation was observed when the sessile droplet was substantially larger than the impacting droplet.
- A gradient of wettability on the substrate showed potential for enhancing droplet mixing.
Conclusions:
- Droplet size ratio significantly influences the mixing process and the formation of hydrodynamic structures like vortex rings.
- Surface wettability engineering offers a promising strategy to control and enhance mixing in droplet-based systems.
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